Fabrication And Properties Of Nanotubular Clay Materials Templated By Natural Cellulose Substances

Among the rich varieties of natural substances, cellulose substance is one of the most abundant organic raw materials. With the assistant of the hydrogen bonds, the polymer chains assemble into microfibrils and microfibril aggregates, and further bundle to form a randomly crossed network of fibres in cellulose substances (such as paper, cotton, wood, cloth and so on). Natural cellulosic materials have been widely used as template to fabricate advanced functional nanomaterials because of their fascinating structural properties. Clay as a naturally occurring mineral, is widely used in every aspect of society due to its unique physical and chemical properties. Therefore, combination of cellulose substance and clay to build advanced functional materials is a promising method.Herein, we employed natural cellulose substances as template and exfoliatied nanoclay as raw materials to fabricate hierarchical nanotubular clay materials, clay composite fiber materials possessing good efficiency of decoloration of aqueous methylene blue and hierarchical nanotubular iron nanoparticles-clay hybrid materials through combination of the surface sol-gel process and layer-by-layer self-assembly method. The details are as follows:1. The fabrication of hierarchical nanotubular clay materials. A series of hierarchical nanotubular clay materials were fabricated by using natural cellulose substance (commercial filter paper) as template. Cellulose nanofibers of the filter paper were firstly coated with ultrathin titania gel films by means of a surface sol-gel process, followed with layer-by-layer self-assembly of poly(diallyldimethylammonium chloride)(PDDA) and the specific clay nanosheets (kunipia-F, montmorillonite-K10and sumecton-SA) through electrostatic interaction. The as-deposited cellulose/titania/polymer/clay composite sheets were calcined in air to remove the cellulose and polymer components, resulting in bulk nanotubular titania/clay hybrid materials, which possessed the sophisticated structures and hierarchical morphologies of the template cellulose substance. Further sulfuric acid solution treatment of the resulting titania/kunipia-F hybrid sheet to remove the titania component resulted in pure nanotubular structured kunipia-F material. Other than calcination treatment, the cellulose template was dissolved away by low-temperature sodium hydroxide/urea solution treatment from the as-prepared cellulose/titania/polymer/kunipia-F composite sheet, yielding nanotubular structured titania/polymer/kunipia-F hybrid material. The walls of the calcined titania/kunipia-F nanotubes were nanoporous due to the removal of the polymer layers, to which gold or silver nanoparticles were induced to give clay-nanotube/metal-nanoparticle hybrids.2. The fabrication of clay composite fiber materials used in decoloration of aqueous methylene blue. Employing a repetitive surface sol-gel technique, an ultrathin TiO2gel film can be deposited onto the surface of the nanofibers of cellulose substances. Afterwards, alternative deposition of PDDA and clay nanoplatelet onto the TiO2film-procoated cellulose nanofibers by layer-by-layer self-assembly through electrostatic interaction. Then, zero-valent iron nanoparticles (Fe-NPs) were immobilized onto the as-prepared cellulose/titania/PDDA/kunipia-F composite sheets via in-situ reduction, resulting in a new composite material cellulose/titania/PDDA/kunipia-F/Fe-NPs showing good efficiency of decoloration of aqueous methylene blue.3. The fabrication of hierarchical nanotubular iron nanoparticles-clay hybrid materials. The nanotubular iron nanoparticles-clay hybrid materials were prepared by using two different methods. Firstly, the as-prepared cellulose/titania/PDDA/clay/Fe-NPs were calcined to obtain hierarchical nanotubular iron oxide nanoparticles-clay hybrid materials (titania/clay/FeaO3). Secondly, the obtained nanotubular titania/clay composite sheets were directly decorated with zero-valent iron nanoparticles by in-situ reduction, resulting hierarchical nanotubular titania/clay/Fe-NPs hybrid materials. All the nanotubular iron nanoparticles-clay hybrid materials faithfully inherited the sophisticated structures and hierarchical morphologies of the original cellulose substance, and possessed ferromagnetic properties thanks to the existence of iron composition.